Improvements in semiconductor fabrication techniques call for new methods to process those semiconductor workpieces. For example, previously, a semiconductor device may be planar, where each surface of the device could be processed since there was a line of sight to the surface to be processed. In other words, an ion beam could be directed, either perpendicularly or at an angle toward the workpiece to strike the specified surface.
However, semiconductor devices now include much more complex structures, such as finFETs and nanowires. These are three dimensional structures, which may involve non-line-of-sight processing to process the surfaces of these structures. In other embodiments, true conformal processing may be beneficial. As an example, a three-dimensional structure may be created in which one surface cannot be impacted by an ion beam because one or more other surfaces may obstruct the path to that surface. Consequently, this surface may be less processed than other surfaces, leading to sub-optimal performance of the device.
For example, a finFET device includes a raised drain structure, extending upward from the surface of the workpiece, and a corresponding raised source structure. A channel region is used to connect the raised drain structure and the raised source structure. In certain embodiments, the channel region extends upward from the surface of the workpiece. However, in other embodiments, the channel region may not extend down to the surface of the workpiece. This channel region, for example, may obstruct an ion beam from reaching other surfaces of the finFET. Because of this, the resulting finFET may not be optimally doped, lowering its performance.
Therefore, it would be beneficial if there were a method of performing non-line of sight processing of a workpiece. Further, it would be advantageous if there were a method of conformally doping all of the exposed surfaces of a device on a workpiece. Further, it would also be advantageous if this conformal doping may be selectively performed on selected surfaces of the device.